"09 HHR LT 2.4L w/76K miles, automatic
Trans seems to surge at about 30 mph. With AC off. Not noticeable on tach but still can be felt.
[ this is 2nd transmission is this vehicle - replaced by dealership at 32k miles with GM factory rebuilt unit ] -
Any thoughts on cause other than another bad transmission.

 

Fairly common complaint. Some have found relief by having the TCM reset with a scantool so it relearns. Most just avoid driving at 30 MPH, that's when the trans wants to go into locked mode but the engine is not ready, so it starts searching.

 

X2 as Donbrew states, look for loose connections at the TCM, loose ground wire, surging could be a dirty throttle body or MAF sensor

 

Thanks for the info. I will try the scantool 1st.

 

Mines done that for the past 150,000 miles lol

 

BTW, scantool mean professional scanner/computer like a Tech2.